1. Field of the Invention
This invention is directed to the field of hardware for use with drills, and, more particularly, to a sleeved stop for a drill bit.
2. Description of Related Art
Drills are common hand tools. They are used in many applications, from home repair to surgery. One common problem associated with the use of drills is that it may be difficult to identify the desired depth of a hole being drilled. In some applications, such as installing door hinges, attaching legs to a table, or during surgery (e.g., dental surgery, neurosurgery, orthopedic surgery, or maxillofacial surgery), drilling the hole to a precise depth is of crucial importance, and so precise control of the depth of penetration of the drill bit is essential.
In simple applications, crude means have existed for providing a stop for the drill bit. In carpentry, for example, it is common to provide a visual stop for a drill bit by applying a long piece of masking tape to the exterior of the bit itself, whereby the edge of the tape closest to the tip of the drill is aligned with the desired maximum depth of penetration of the bit. The tape can also be wrapped about the bit several times to establish a shoulder which abuts the surface into which the drill penetrates. This functions to limit the travel of the bit beyond the desired depth. While this approach works satisfactorily in carpentry, it is not appropriate, for example, in oral surgery, where a more precise (and sanitary) form of stop is needed.
The prior art includes many known stops for drill bits. For example, U.S. Pat. No. 5,078,552 (Albel) shows a stop for a drill bit for regulating the depth to which a drill bit may extend. The stop is friction-fit to the exterior of a standard drill bit, and may be secured in place by securing the end of the bit to the drill. The stop, however, does not provide any means for finely controlling the precise depth to which the bit may extend.
Another known stop is shown in U.S. Pat. No. 5,152,792 (Watkins, et al.) which shows a sleeved stop to limit the depth of penetration of the bit. The stop is threaded and may be set to the desired depth but it does not provide a means of fine adjustment, as the threads are widely spaced. Alternatively, if the threads are finely spaced, coarse movements would be difficult, since many turns of the thread would be required to move the stop larger distances.
U.S. Pat. No. 4,710,075 (Davison) shows a stop for a surgical drill bit, in which the depth of penetration is limited by a frusto-conical stop attached to the exterior of the drill bit. The top of the drill bit (i.e., the part farthest from the tip of the bit) includes a series of parallel grooves, with which a plunger (set screw) engages to secure the stop against movement. This suffers from the drawback that the adjustment of the depth of the hole to be drilled is limited by the distance between the grooves. The depth cannot be adjusted, for example, to one-half the distance between adjacent grooves, as the plunger will not be engaged and would therefore be subject to movement.
Accordingly, there is a need in the art for a drill bit stop which provides means for reliably and precisely setting the depth of penetration of a drill bit, while preserving ease of use and adjustment for making both coarse and fine adjustments to the drilling depth.